<First Background Art>
Conventionally, in fields of hybrid vehicles, electric vehicles, household electrical appliance, industrial equipment, and medical equipment, there have been used signal transmission circuit devices using an isolator for isolating direct current between input and output while transmitting a signal.
FIG. 19 illustrates a conventional drive circuit device for a power semiconductor for driving a motor mounted in a hybrid vehicle, for example, and a signal transmission circuit device used for the drive circuit device. A drive circuit device 100 for the power semiconductor includes an electronic control device 102, a signal transmission circuit device 104, a power semiconductor 106, and a motor 108.
The electronic control device 102 generates a control input signal for controlling the motor 108 mounted in a hybrid vehicle, for example, via the power semiconductor 106. The electronic control device 102 corresponds to an engine control unit (ECU) in this type of technical field.
The signal transmission circuit device 104 includes a transmission pulse generating circuit 110, an input signal transmission unit 112, and a reception circuit 114. The input signal transmission unit 112 includes a photocoupler or a transformer (not shown) as an isolator for isolating direct current between an input side circuit and an output side circuit of the signal transmission circuit device 104.
FIG. 20 illustrates a signal transmission circuit device disclosed in FIG. 1 of Patent Document 1. A signal transmission circuit device 120 includes a glitch filter 122, edge detectors 124 and 126, an inverter 128, transformers 130 and 132, and a flip-flop 134.
The transformer 130 has a primary winding 130A and a secondary winding 130B, and the transformer 132 has a primary winding 132A and a secondary winding 132B. The primary windings 130A and 132A are connected to ground potential A (GND A), and the secondary windings 130B and 132B are connected to another ground potential B (GND B) that is isolated for direct current from the ground potential A.
In addition, with reference to FIG. 8 of Patent Document 1, a transmission circuit 802 and the ground potential A (GND A) are disposed on a first substrate 804, while a top coil 806A having a function as the primary winding, a reception circuit 810, a bottom coil 806B having a function as the secondary winding, and the ground potential B (GND B) are disposed on a second substrate 808. Thus, a technical concept of forming an isolator including a transformer on an IC chip is disclosed in Patent Document 1.
FIG. 21 illustrates a signal transmission circuit device disclosed in FIG. 7 of Patent Document 2, in which reference numerals are changed.
Patent Document 2 discloses a technical concept of correcting mismatch between the control input signal and the control output signal by regularly generating a refresh pulse in the input side circuit.
A signal transmission circuit device 140 includes Schmitt trigger inverters 142 and 150, an input signal encode circuit 144, a transformer 146, and an input signal decode circuit 148, and further includes an input signal updating circuit 152 and a watchdog circuit 154. The input signal updating circuit 152 regularly generates the refresh pulse so as to update the control input signal. The watchdog circuit 154 detects an abnormal state in the circuit device and controls shutdown or the like of the control output signal.
<Second Background Art>
FIG. 33 is a schematic diagram illustrating a conventional example of a semiconductor device in which a coil is integrated. A semiconductor device Y10 of this conventional example includes a coil L1, and pads Y11 and Y12. Note that both ends of the coil L1 are connected to the pads Y11 and Y12, respectively.
FIG. 34 is a schematic diagram for explaining defective inspection of the semiconductor device Y10. An inspection apparatus Y20 used for defective inspection of the semiconductor device Y10 includes probes Y21 and Y22, a constant current source Y23, and a voltmeter Y24. Note that one end of the constant current source Y23 and one end of the voltmeter Y24 are connected to the probe Y21, while the other ends of them are connected to the probe Y22.
Conventionally, in the defective inspection of the semiconductor device Y10, the probes Y21 and Y22 are made to contact with the pads Y11 and Y12, respectively, and a predetermined constant current I is supplied from the constant current source Y23 to the coil L1. Then, a voltage generated across the coil L1 (voltage drop generated due to a series resistance component RL of the coil L) is measured by the voltmeter Y24 so that a break of the coil L1 is checked. Specifically, if the voltage across the coil L1 cannot be measured normally, it is decided that the coil L1 is broken, and the semiconductor device Y10 is rejected as a defective product.
Note that there is Patent Document 3 as an example of a conventional technique related to the semiconductor device in which a coil is integrated.
<Third Background Art>
FIG. 43 is a circuit block diagram illustrating a conventional example of the signal transmission device, and FIG. 44 is a timing chart illustrating an example of the normal operation. A signal transmission device 100 of this conventional example includes a transformer drive signal generating portion 101, a transformers 102a and 102b, comparators 103a and 103b, and an SR flip-flop 104, and realizes signal transmission between a primary side circuit and a secondary side circuit while isolating between a ground voltage GND1 of the primary side circuit and a ground voltage GND2 of the secondary side circuit by using the transformers 102a and 102b. 
The transformer drive signal generating portion 101 generates transformer drive signals S10a and S20a, and outputs the same to primary side windings of the transformers 102a and 102b, respectively. Note that the transformer drive signal generating portion 101 generates one pulse via the transformer drive signal S10a using a rising edge of an input signal IN as a trigger, and generates one pulse via the transformer drive signal S20a using a falling edge of the input signal IN as a trigger.
The transformers 102a and 102b respectively generate induced signals S10b and S20b corresponding to the transformer drive signals S10a and S20a in secondary side windings thereof.
The comparators 103a and 103b respectively compare the induced signals S10b and S20b with a predetermined threshold voltage to generate comparison signals S10c and S20c, and hence output the signals to a set input terminal (S) and a reset input terminal (R) of the SR flip-flop 104, respectively.
The SR flip-flop 104 sets an output signal OUT to high level using a rising edge of a comparison signal S10c as a trigger, and sets the output signal OUT to low level using a rising edge of a comparison signal S20c as a trigger.
Therefore, if a normal signal transmission operation is performed, the output signal OUT from the SR flip-flop 104 becomes the same signal as the input signal IN input to the transformer drive signal generating portion 101.
Note that there is Patent Document 1 as an example of a conventional technique related to the above description.